Magnetic control device



Sept. 20, 1938. E. w. BOEHNE MAGNETIC CONTROL DEVICE Original Filed Aug. 4, 1936 2 Sheets-Sheet l Imventor. EugeneW.Boehne,

His Attorney.

Sept. 2@, 393 8. E. w. BOEHNE 2,139,372

MAGNETIC'CONTROL DEVICE Original Filed Aug. 4, 1936 2 Sheets-Sheet 2 Fig.4.

H is Atto rrw ey.

Patented s... 2c, 1938 UNITED STATES PATENT OFFICE MAGNETIC CONTROL DEVICE Eugene W. Boehne, Yeadon, Pa, assignor to General Electric Company, a corporation of New York 5Claims.

My invention relates to improvements in magnetic control devices and more particularly to control devices for large capacity, high voltage circuit breakers whereby to provide improved and 5 high speed control for opening the circuit breakers.

This application is a division of my application, Serial No. 94,219, filed August4, 1936 for Control devices and systems.

Large capacity, high voltagecircuit breakers for transmission lines such as the 287.5 kv. lines extending from Boulder Dammust open quickly, particularly under faulty line conditions. High speed circuit breakersfor this kind of service require such large forces for opening and closing that a separate operating mechanism for each pole of the circuit breaker is practically neces sary, particularly from the standpoint of shocks and jars in operation. Naturally the cost of building high operating speed into circuit breakers is considerable. This high speed operation of the circuit breaker would of course be sacrificed by the slow operation of a single trip co l operating on a common trip lever. For hiih speed operation, a flux opposition type of trpping coll mechanism such as is disclosed in my application, Serial No. 94,220 filed August 4, 1936, for High speed permanent magnet trip for circuit breaker may be used for each pole of the circuit breaker. Such single pole tripping mechanisms require a tripping current of the order of 40 amperes D. C. Thus for a three-phase circuit the .trip current would be about 120 amperes.

Existing fault responsive protective relays and particularly high speed relays are not built to handle such large currents. Even if they could be so built on an economical basis, it would probably be at a sacrifice in their speed and protective features. 7

40 In accordance with my invention, I provide a high speed, large current capacity, magnetic control device which can be readily controlled by any high speed fault responsive relay or otherwise to efiect the tripping of a high speed circuit breaker in a time commensurate with the circuit breaker opening time. This and other objects of my invention will appear in more detail hereinafter.

My invention will be better understood from the following description when considered in connection with the accompanying two sheets of drawings, and its scope will be pointed out in the appended claims.

In the accompanying drawings, Fig. 1 is a front elevationoi a control device embodying my for maximum attractive force and which, upon 10 being moved to the attracted position, is maintained therein against the bias of suitable means such as springs I l by a magnetic structure forming a main flux path and comprising a magnetic element I2, polar extensions i3, and pole pieces l5 M. This magnetic structure is so designed as to produce, at the armature, a flux which produces the maximum attractive force for the optimum armature area. while I may use an electromagnetic structure with a suitable energizing 2o winding on the element I2, I have chosen, in the illustrated embodiment of my invention, to show this element as a permanent magnet, since the use of such avoids the losses in energy and dimculties due to heating attendant upon a device 25 continuously energized by electric current. The device is, therefore, particularly adapted to locations where battery potential is at a premium In order to combine maximum coercive force with minimum space requirements, the magnetic 30 element l2 may be an aluminum-nickel-cobalt iron alloy, such as disclosed, for example, in United States Letters Patent No. 1,968,569, issued July 31, 1934, on an application filed by W. E.

' Ruder. 35

For control purposes, the armature i8 is suitably mounted, as, for example, on a pivoted yoke l5 whi h carries a contact Hi. This contact coopere .es with a suitably mounted and adjustably positioned contact l'l. In the particular arrange- 4 ment illustrated by way of example, the contacts I6 and ii engage upon movement of the armature I0 from the attracted position under the bias of the compression springs ll, although it will be obvious that this movement of the arma- 45 ture could just as well effect a contact separation, if desired. In order to obtain high speed of operation, the contact gap may be relatively small, for example, of the order of one thirtysecond of an inch and the spring bias large. 50 This latter feature naturally requires a relatively large magnetic force to hold the armature in the attracted position, as well as a greater force to move it to the attracted position.

In order to actuate the armature for contact 55 .member i8 are polarized similarly controlling movements thereof, I provide means for opposing the flux of the magnetic structure in the armature sufliciently to efl'ect the release thereof and for increasing the flux in the armature when in the unattracted position sumciently to return the armature As shown, the flux changing means includes an auxiliary or shunt fiux path, such as a magnetic member [8, which is arranged to be energized by one or more windings 19 and 20. If the inner or releasing winding l9 be energized by a unidirectional current in such a direction that the ends of the shunt magnetic member I 8 are polarized oppositely to the permanent magnet .I2, then the flux of the magnet l2 in the armature in will be so opposed as to effect the release and movement of the armature to the unattracted position under the bias of the springs II. If now the inner winding l9 or another winding, such, for example, as the outer winding 20, be

energized by a unidirectional current in such a.

direction that the ends of the shunt magnetic to the permanent magnet [2, then enough flux will be added to that already passed through the armature I 0 by the magnet l2 to move the armature to the attracted position against the bias of the springs II. or course, in the attracted position the additional flux is not required because of the air gap reduction. Consequently, the reset winding 20 need not remain energized. In order to expedite flux changes in the armature l0 and the pole pieces I 4 which the armature engages so asto obtain the quickest response, these parts are, as shown more clearly in Fig. 1, preferably laminated, the magnetic path is made as short as possible, and the armature contact area is the optimum. To further expedite the speed of operation, the releasing winding i 9 is designed with an optimum number of turns, such that the flux required to trip the armature can be established in the fastest possible time for the voltage available. Because of the relatively few turns required to satisfy this condition, the resistance of the releasing winding I8 is correspondingly low and the current in the winding circuit must be limited by suitable means such as an external resistance 21 connected in series with the winding.

It will be apparent from the configuration of the magnetic structure that when the coil [9 is energized, it produces a flux flow, roughly in the form of a figure 8. Part of this .flux is in the same direction as the flux in the permanent magnet I2 and is therefore additive. and part opposes the flux in the armature I 0, thereby causing the armature to be released under the action of the biasing springs II. The paths and magnitudes of all fluxes can be calculated separately, and the net flux in any path follows the simple laws of superposition or algebraic addition. In the device under consideration, the' major part of .the flux of the winding 19 flows in the short low-reluctance laminated circuit. of the armature l0, instead of in the longer massive high-reluctance circuit of the permanent magnet I 2. The use of a mag netic alloy, such as heretofore mentioned, is therefore'desirable, since its reluctance is a great many times that of the steel core of an equivalent electromagnet. This allows a higher percentage of the trip coil flux to flow in the armature circuit hence producing faster flux neutralization and faster tripping.

As illustrated, the foregoing magnetic structure is assembled in a compact form and held together by a suitable means, such as a bolt 2|. Upper and to the attracted position.

' shown, on which the trip coil 49 of a protective relay II or the The armature pivot 25 may be mounted on a supporting plate 26 secured to the lower pole piece l3. Resistances 21 may be mounted on the lower bracket 23. As shown, the adjustably positioned fixed contact I! is mounted on but insulated from the upper pole piece l3. A transverse member 30',.which is secured to the armature yoke i5 and bears against the outer ends of the springs ll, serves as a support forthe movable contact I6, which is suitably insulated. The movable contact l6 is'connected through a flexible lead 28 to a stationary terminal 29, also mounted on but insulated from the upper pole piece I 3. The springs I I arecarried on an adjustably positioned plate member 30 which is supported by the upper bracket 22.

Referring now to Fig. 4, which diagrammatically illustrates an em ent of my invention as applied to a circuit breaker control scheme, each of the conductors 32 of a polyphase circuit is provided with a. single pole circuit breaker 33 which may have its own independent closing mechanism. So far as my invention is concerned, the type of circuit breaker is immaterial, but in general, it will be a high speed circuit breaker provided with some means, such as the latch 34, for holding it closed against an opening bias and a trip coil 35 for releasing the latch under predetermined circuit conditions or otherwise. However, for purposes of illustration, I have shown in schematic form a tripping magnet such as is disclosed in my aforesaid application, Serial No'. 94,220. This tripping magnet comprises an armature 50 pivotally secured to the latch 34, a permanent magnet 5|, laminated pole pieces 52 against which 7 the armature seats in the attracted position, and

a shunt flux establishing path such as a core, not 35 is mounted. A supplementary trip coil 35', similar to the trip coil 35, may also be provided on the shunt flux path. It will be apparent that the features of magnet construction are exactly the same as those of my magnetically controlled device heretofore described. -Since the condition of optimum turns in the trip coils 35 and 35' render these windings of relatively low resistance, suitable current limiting means such as resistances 53 and 53', respectively, may be included in series with these coils. Each circuit breaker may be provided with auxiliary'switching means, such as contacts 33.

36', 31 and 31', which are closed when the circuit are open when the circuit breaker is closed, and

vice versa. For reasons which will appear hereinafter, it is necessary that none of the contacts as closes until after the contacts as and :1 of the same circuit breaker are open.

For energizing all of the trip coils 35 simultaneously so as to trip all circuit breakers at the same time, the trip coils 35 may be connected in parallel to one side of the control bus; positive in the drawings, through'the respective circuit breaker auxiliary contacts 36 and to the other side, negative in the drawings, of the control bus through the contacts i8 and I! of a control device'like that shown in Figs. 1, 2, and3. For controlling this device in response conditions or otherwise, the releasing winding I! may be connected in a-circuit from one side of the control bus through all the circuit breaker auxiliary switch contacts 31 in series, the contacts contacts 42 of a to predetermined circuit the resistance 21 to the other or negative side of the control bus. Obviously, the protective relay 41 may be of any suitable type for the purpose atv hand, and any number of protective relays may be employed with their contacts in parallel or otherwise depending-upon the particular scheme of protection. However, for simplicity, there is.

shown only one protective relay of the simple over-current type energized from a current trans former 44 in one of the phase conductors 32. The resistance fl is included inorder to reduce the current in and also the time constant of the circuit of the releasing winding 19, whereby to hasten the build-up of flux by this winding, and thereby increase the speed of action of the device. In order further to accelerate the build-up of a large flux in the releasing winding I9 so as to speed the action of the device, there may be included across the control source a capacitance 45, which is normally charged and so connected as to discharge into the winding i9 upon the closing of the contacts 40 of the protective relay or the contacts 42 of the trip switch 43. In this way, the condenser 45 acts as a supplemental energy reservoir for the trip coil IS in addition to the current which flows in the winding from one side of the bus to the other- For the same purpose, there may be connected in like manner across the trip coils 35 and the contacts l6 and I1 oi the control device a .capacitance 54 which, as shown, is connected between the end of the resistance 53 nearer the trip coils 35 and the positive control bus.

The arrangement is such that, upon the opening of all the circuitbreakers, the control device is reset; that is, its armature I0 is restored to the attracted position with the contacts l6 and i! open. For this purpose, there is provided anauxiliary relay 46, whose contacts 41 control the circuit of the reset winding 20. The circuit of the auxiliary relay winding is through the circuit breaker auxiliary contacts 38 in series so that thisrelay can not be energized until all the circuit breakers are fully tripped and opened. This relay 45 is shown in Figs. 1 and 2 as of the hinged armature type and may be mounted on the base 24 in any suitable manner. A current limiting resistance 48 may be included in series with the winding of this relay depending upon the voltage rating of its windings and the voltage of the control source.

Assuming the parts positioned as shown in Fig. 4 and that a fault on the circuit 32 effects the operation of the protective relay 4| or that the switch 43 is operated to close its contacts, then the circuit of the tripping winding i9 will be completed through either the contacts 46 or 4?.

This winding quickly builds up its opposing flux by virture of the small time constant of the circuit oi the winding and the discharge of the charged capacitance 45 whereby to release the armature 10 so as to close the contacts l6 and I1. As soon as these close, all of the trip coils 35 are immediately connected in parallel across the control buses through the respective circuit breaker auxiliary contacts 39 and the condenser 54 discharged into the trip coils whereby to trip the circuit breakers very quickly. As soon as the circuit breakers have all opened, t. e auxiliary switch contacts 36 will be opened to interrupt the trip coil circuits and the auxiliary switch contacts 38 will be closed to complete the circuit of the auxiliary relay 46 through the closed con tacts l6 and ll of my control device, whereby to the reset winding 20 is completed, whereby to increase the amount of flux in the armature ll sufliciently to move the armature to the attracted position andopen the contacts and I1. As soon as these contacts are open, the circuit of the auxiliary relay 45 is opened, and this relay opens its contacts 41 whereby to tie-energize the circuit of the reset winding 20. The armature J0, having been moved to the ,attracted position, remains in this position by virtue of the flux established by the permanent magnet. l2 and everything is in position ready for reclosing the circuit breaker to efiect a subsequent tripping operation as desired. 7 r

The supplementary trip coil 35' may be provided when it is desired to open every circuit breaker in case one circuit breaker opens accidentally for any reason whatsoever, such, for example, as mechanical failure, latch failure, and the like. Thus, the circuits of the supplementary trip coils 35' may be so arranged as to eiiect the energization of these trip coils whenever one cirbreakers.

While I have shown and described my invention in considerable detail, I do not desire to be limited to the exact arrangement shown, but seek to cover in the appended claims all those modifications that fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by 4 Letters Patent oi the United States is:

1. A magnetic device comprising an armature,

a magnetic structure for maintaining said armature in the attractedposition after it is moved to said position, means biasing said armature for movement vfrom said position, a shunt flux path for said armature, means for establishing a flux in said path in a direction to decrease the flux in said armature whereby to effect a release of the armature, and means for establishing a flux in said path in a' direction to increase the flux in said armature whereby to return the armature to the attracted position.

2. A magnetic device comprising an armature, a permanent magnet for maintaining said armature in the attracted position after it is moved to said position, means biasing said armature for movement from said posit-ion, a shunt flux path establishing an additional magnetic circuit for said armature, electromagnetic means for establishing a flux in said circuit in a direction to oppose and decrease the armature flux from said permanent magnet whereby to effect the release of the armature and electromagnetic means for establishing a flux in said circuit in a direction to add to the armature flux whereby to return the armature to the attracted position.

3. A magnetic device comprising an armature, a magnetic structure including a main flux path for maintaining said armature in the attracted position, means tending to move said armature from said position, an auxiliary flux path for said armature, means for establishing a fluxin said "a magnetic structure including two flux paths common to said armature for controlling the positioning thereof, means for establishing a flux in one of said paths to hold the armature in the attracted position, means tending to move the armature from the attracted position, means for establishing a flux in another of said paths in a direction to decrease the flux in said armature whereby to effect a release of the armature, and

means for establishing a'flux in one of-said paths whereby to return the armature to the attracted position.

5. A magnetic device comprising an armature, a magnetic structure including two flux paths common to said armature for controlling the positioning thereof, means for establishing a flux in one of said. paths to hold the armature in the attracted position, means tending to move the armature from the attracted position," means for establishing a flux in another of said paths in a direction to decrease the flux in said armature whereby to effect a release of the armature, and

means for establishing a flux in said other path for increasing the flux in said armature'suificiently to return the armature to the attracted position.

EUGENE W. BOEHNE. 

